Maybe I’m just relieved that it wasn’t in 3-D, or maybe actor Justin Theroux (frequent David Lynch collaborator and co-scripter of Tropic Thunder) is just a better writer than the law firm of scribes that pasted together the original, but Jon Favreau’s sequel to his creaky adaptation of the rusty Marvel standby Iron Man restores my lack of faith in superheroes. The show starts out with a fireworks display and for the next two hours pretty much continues along those lines, but from the noise and flash and glib dialogue, a coherent intelligence emerges, a sly (pun unintended but unavoidable) irony that undermines the übermensch, messianic appeal of the genre.

All of which would not be possible without the return of Robert Downey Jr. as Tony Stark, everyone’s favorite overbearing, charismatic billionaire demigod. We rejoin him just as he has — like a steel-clad Dr. Manhattan from the ill-fated Watchmen — saved the world from itself through the power of his omnipotent “high-tech prosthesis.” That’s how he describes his RoboCop-like duds to the Senate committee investigating whether or not it’s a good idea to relinquish the entire defense of the country and the security of the whole world to one jokey, hedonistic asshole with a mechanical heart and a lot of unresolved father issues. What worries the pols, though, is not that Stark might take it into his head to become dictator for life, but that the North Koreans or the Iranians might dump their nuclear programs for knockoffs of SItark’s designer duds.

Stark, meanwhile, despite his insouciance and insufferable egotism, is living on borrowed time. The power pack operating his ticker and his suit afflicts him with something like nuclear acid reflux. He needs a vacation, but that’s not likely with the threat developing (unbeknownst to him) in a boozy garret in grim, snowy Moscow. There, the vengeful Ivan Vanko (Mickey Rourke, who, in a film dominated by bloodless violence and pristine CGI, seems as if he might actually smell) works furiously with primitive equipment — as Stark himself did in the original film — and develops his own prototype power suit.

The outfit looks like something left over from Mad Max Beyond Thunderdome, with the extra dominatrix touch of electrified whips, and it gives Iron Man all he can handle in their first round together. In a sequence involving bisected racing cars, a limo used as a battering ram, and Gwyneth Paltrow as Pepper Potts wielding a suitcase, it’s the first of many spectacular action scenes. Unlike Michael Bay and the directors of just about every other summer blockbuster made since at least The Rock, Favreau understands that such scenes work much better if the shots are held long enough for them to at least register on the retina. Whether the combatants are Stark and his pal Lt. Colonel Rhodes (Don Cheadle) working off steam battering away at each other in Iron Man suits like Rock ’Em Sock ’Em Robots, or Scarlett Johansson in a leather jumpsuit mopping the floor with a platoon of hired goons, or dozens of battleship-like drones flying off like Roman candles, the battles possess their own daffy clarity and logic.